This application claims a priority from German patent application No. 100 54 517.3, filed on Nov. 3, 2000, the contents of which are incorporated by reference herein.
This invention concerns a method for synchronization of CDMA signals. For a CDMA (Code Division Multiplex Access)—method, a plurality of orthogonal codes are simultaneously transmitted. In this manner, symbols are divided in a known manner so that each symbol is of a plurality of chips. In this regard, there is the necessity to carry out a so-called Pilot Synchronization. For a Pilot Synchronization, an input-chip-sequence is compared with a known pilot-chip-sequence in order to determine a displacement, or shift, (offset) between the input-chip-sequence and the pilot-chip-sequence, which is generally referred to as the pn-sequence. To determine this offset for a standard IS-95, for example, information in a pilot channel having the characteristic that the symbols as well as also a Walsh-code is a constant 1 is utilized and thus only the pn-sequence is present.
The synchronization of the input-chip-sequence with the pilot-chip-sequence (pn-sequence) usually is carried out by correlation. The pn-sequence has a periodicity, or frequency, of 215 chips and is, therefore, relatively long. A direct correlation of the input-chip-sequence with the pilot-chip-sequence, when using a hardware implementation, leads to a relatively high logic gate requirement. And, upon a software implementation, it leads to a relatively long calculation time.
It is, therefore, an object of this invention to provide a method for synchronizing an input-chip-sequence of a CDMA signal with a pilot-chip-sequence that can be carried out in a short calculation time because of an efficient algorithm.